Books like Backtrack by Betsy Brannon Green

A missing Mormon child leads Wyoming Sheriff Longmire and Deputy Victoria Moretti, with friend Henry Standing Bear, on a high‑plains hunt that uncovers a violent interstate polygamy group.

In 1919, nurse‑in‑training Kitty Weekes infiltrates Portis House, a crumbling war hospital turned haunted estate, where shell‑shocked soldiers dream of a shared nightmare. Together with a mysterious inmate, she uncovers supernatural forces and a deadly secret.

"I very much need to be dead." These are the chilling last words left by a man who had everything to live for but took his own life. In the void that remains stands his widow, FBI agent Jane Hawk, surrounded by questions destined to go unanswered unless she does what all the grief and fury inside her demand: Find the truth, no matter what. People of talent and accomplishment, people seemingly happy and sound of mind, have recently been committing suicide in surprising numbers. A disturbing pattern is beginning to emerge. Jane is determined to give up everything to find out why. And if that means going rogue and becoming America's Most Wanted, then so be it. Those arrayed against her are legion, and devoted to protecting something profoundly important-or terrifying-enough to exterminate any and all in their way. But Jane is as clever as these enemies are cold-blooded, as relentless as they are ruthless. And she is driven by a righteous rage they can never comprehend. Because it is born of love.

In 1814 Darbury, an heiress defies expectations to raise her friend’s dying infant, even courting the child’s sea‑captain father to keep her promise.